What is g-sensitivity in an Oscillator?

The change in output frequency of a crystal oscillator due to applied acceleration is called g-Sensitivity. It is also called acceleration sensitivity and is expressed in terms of ppb/g. It is the oscillator's inherent sensitivity to external forces applied in any direction. As oscillators are used in timing electronics for a wide range of daily applications, precision is an important factor when selecting oscillators. G-sensitivity of the oscillator helps determine the accuracy and resolution sensitivity of oscillators in environments where there can be excessive acceleration. Some areas where this is an important factor include spacecrafts, rockets, airplanes etc.

Oscillators are electro-mechanical devices that use crystals like quartz in their construction. When a voltage is applied to a crystal it oscillates at a particular frequency. This frequency is reproducible and very accurate. However, a number of real-world factors can cause it to deviate from its ideal value. g-sensitivity is one of those factors. The magnitude of this phase noise or frequency deviation is directly proportional to the amount of force or acceleration applied - the higher the force, the greater the frequency instability and the greater the phase noise induced. Hence, G-sensitivity is key in determining the frequency stability of an oscillator.

There are different types of crystals used in oscillators like AT cut, IT cut, SC cut etc. Quartz crystals have different costs and precision according to their cut type. The SC cut crystal type has lower g-sensitivity due to a stress compensation feature. The g-sensitivity for bulk mode quartz crystal range from less than 1x10^-10 per g for the precisely made SC cut crystal to greater than 1x10^-7 per g for low-cost AT cut crystal type. Hence, the quality of crystals used in oscillators also helps determine their g-sensitivity.

everything RF has listed low-g sensitivity crystal oscillators from the leading manufacturers:

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